CHROMATOGRAPHIC-PHOTODENSITOMETRIC QUANTITATION OF THE SOLANACEOUS ALKALOIDS
Bibliographic record
Abstract
The thesis work has involved an attempt to improve the accuracy and precision of direct photodensitometric quantitation of thin-media chromatograms. Direct photodensitometric evaluation of paper and thin-layer chromatograms has been used increasingly in the past decade and is now accepted as a standard method of estimation. The bulk of the methods published have been highly empirical in nature. Recently, there has been considerable disenchantment with all types of in situ analysis and there is now considerable interest in developing a theoretical basis for optical assays performed in situ. Little attention has been paid to the fact that the absorbance varies considerably throughout a spot and that the geometry of "'inhume spots may vary considerably from that of standard spots be- cause of the greater complexity of unknown samples. It was felt that the only way to reduce errors of non-linearity due to non-uniform distribution of substance over the illuminating slit and compensate for distortions in spot geometry would be to replace fixed-slit scanning by two-dimensional scanning of spots with a small point of illumination. Because a two-dimensional or "flying-spot" scanner was not available, two-dimensional scanning was simulated by manual collection of density data using a 1 x 1 mm. optical slit over the entire area of the spot, integration being accomplished by summing all data points. Experimental work was done on the Solanaceous alkaloids which were separated electrophoretically on cellulose thin-layers and stained with Dragendorff's reagent. The chromatograms were made translucent with mineral oil before scanning in order to reduce the high light-scattering properties of the support media. In order to expedite analysis and make the scanning process more continuous, an analog computer was later built to convert the output potential of the existing photometer (output varying with transmittance) to absorbance (negative log of the transmittance). Two-dimensional scanning was semi-automatic in nature--scanning across the spot was motorized but the chromatogram had to be advanced manually and the scanning stage had to be returned manually for the next pass over the chromatogram. Output of the density signals Was on a strip-chart recorder with continuous, automatic, digital integration of density peaks. Calibration curves (integrated absorbance vs. concentration) produced were quite linear and assay results on "simulated" unknowns and comparative assays on natural products containing the alkaloids under study were encouraging. Further work in this area necessitates better stabilized equipment as well as rapid flying-spot scanning with continuous electronic integration. This would allow improvements in accuracy, not only by allowing more precision in scanning; but would allow the collection and averaging of more data. Well stabilized equipment is necessary for meaningful study of the proportionality of radiative transfer to concentration.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.004 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".